What does theory mean?

The word theory has many different meanings in different branches. The meaning of theory depends on the methodology of these branches. In science, theory is a testable model in order to verify a natural fact or phenomena. A theory can be tested again and again. A theory should base on observation, experimentation and reasoning. Theory is used for signify a conjecture, an opinion or a speculation. A theory does not need to base on scientific facts. It is not to be required totally true. Theory is also a step of scientific method.

http://en.wikipedia.org/wiki/Theory
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